scope in javascript and execution steps

Question

(function() {
            var a = 'g';
            function foo() {
                console.log(a);
                a = 7; //
            }
            console.log(foo(), a);
    }());

Can anybody explain the step by step execution and out put of this code sample. I got the out put as 'g undefined 7'

Answer 1

You are creating an anonymous function and executing right away (IIFE)

Then, in this scope function :

• You declare an a var with value g
• You declare a function named foo which has visibility on parent function scope (IIFE scope). So it can see the a var. This foofunction is not called right away.
• In logstatement, foo is executed :
  • a is logged (value g)
  • a var in IIFE scope is changed to value 7
  • foo returns nothing
• Is then logged :
  • foo returns value which is undefined (no return value)
  • a value, which is 7 after foo is executed.

So you have in your console :

g
undefined 7